This invention relates to the production of esters and in particular to the production t-butyl acetate.
Relevant background information for consideration includes the following, herein incorporated by reference: U.S. Pat. Nos. 3,102,905, 3,644,497, 5,866,714, 5,994,578, PCT WO 99/54276, and U.S. Pat. No. 3,678,099.
The reaction of isobutylene and acetic acid in the presence of an acid catalyst and excess reactant is well known in the art. Tertiary butyl acetate, (xe2x80x9ct-BuAcxe2x80x9d), is typically produced by an acid catalyzed acetoxylation of isobutylene with acetic acid (xe2x80x9cHOAcxe2x80x9d). The reaction mixture containing product t-butyl acetate, unreacted acetic acid, and isobutylene, and by-product isobutylene dimer plus any uncreated feed components, is typically fed to distillation columns for recovery of uncreated feed and the purification of the product t-butyl acetate. There are various factors affecting the production of t-butyl acetate, including but not limited to: operating conditions of the fractional column (e.g., temperature, point of feed, rate of feed, rate of withdrawal of product, etc), and, temperature of the reaction mixture as it is fed to the column. A common occurrence is the buildup of (isobutylene) dimer or neutralized catalyst in the column during the distillation process, leading to sludge formation and ultimately requiring shut down and/or clean out of the column.
It is thus desirable to produce t-butyl acetate with an alternative source of acetoxylation target, or in other words, a material more widely available than pure isobutylene. The traditional problems associated with prior art methods are thereby minimized or avoided as well as the high cost of using purified isobutylene.
The present invention provides an advantage in production of t-butyl acetate from readily available and lower cost Methyl Tertiary Butyl Ether (xe2x80x9cMTBExe2x80x9d), or Ethyl Tertiary Butyl Ether (xe2x80x9cETBExe2x80x9d), as a raw material, compared to the current use of higher cost isobutylene. The present inventive route also utilizes acetic anhydride production, and optionally, methyl acetate hydrolysis.
Disclosed herein is a process for the production of t-butyl acetate and co-production of methyl acetate (MeAc), or ethyl acetate (EtAc), directly from MTBE, or ETBE, by contacting a mixture of acetic acid, acetic anhydride, and MTBE, or alternatively ETBE, with an acid catalyst. The catalyst may be a strongly acidic ion-exchange resin, such as a macroreticular type resin.
Typically the reaction pressure is maintained at about 1 to 5 atmospheres and the reaction temperatures are in a range of from about 10xc2x0 to 100xc2x0 C., with a preferred temperature range being about 40xc2x0 to 70xc2x0 C. However, it will be recognized by those in the art that reaction conditions, including pressures and temperatures, can be varied in accordance with optimal engineering design of the equipment, and operation of the process.
It is preferred to purify the reaction mixture containing t-butyl acetate (t-BuAc), MeAc, or EtAc by fractional distillation or conventional techniques.